Serologic evidence of past infection with a Sin Nombre-like hantavirus(es) was demonstrated in 78 (40.4%) of 193 Indians living in western Paraguay and in 38 (17.1%) of 222 Indians inhabiting the Salta province of northern Argentina. In both populations seroprevalence increased with age, with the most striking increase occurring at 18 years of age in the Paraguayan population and at 35 years of age in the Salta population. The peak prevalences in both populations (66.6% and 44.0%, respectively) were seen in Indians Ͼ 53 years old. Although no sex difference was observed in the Paraguayan Indians, in the Salta population seroprevalence was greater in males than in females. Familiar clustering of the infection was observed. The data indicate that the Indian populations of the Gran Chaco are frequently exposed to and survive infection with a Sin Nombre-like virus(es). Possible explanations of this novel epidemiology are discussed.

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Human T cell leukemia/lymphoma virus (HTLV-II) type II infection was detected by polymerase chain reaction or serologic analyses (or both) in 22% of 697 Indians of six different ethnic back-grounds inhabiting the Argentinean and Paraguayan Gran Chaco. None was infected with HTLV-I. The prevalence of HTLV-II increased with age (14% in those < 13 years and 23% in those > or = 13 years). HTLV-II infection was found in all 20 Gran Chaco communities studied, but marked differences (44%-4%) in the rate of infection were observed even in communities separated by only a few miles. These variations correlated closely with ethnicity. In the high-incidence communities, infection clustered within families, with evidence for both sexual and perinatal transmission, primarily via breast-feeding. By contrast, only 2% of 94 Mapuche Indians from southern Argentina were positive for HTLV-II. Analyses of pol and long terminal repeat sequences from 15 Gran Chaco HTLV-II strains indicated that they constitute a highly conserved branch of the HTLV-IIB substrain.

Se estudió la respuesta clínica y serológica a la infección chagásica de 937 embarazadas y sus 929 recién nacidos (RN) vivos, grupo I; 4 RN de origen diverso, grupo II y 35 RN derivados de otros centros, grupo III. Las embarazadas se estudiaron con 3 reacciones serológicas; se definió infección cuando 2 o más reacciones eran positivas. En los RN el diagnóstico se confirmó por observación directa del T. cruzi en una muestra de sangre. Los RN con Chagas congénita (RN-ChC) fueron tratados y seguidos con estudios clínicos y de laboratorio. Se detectaron 149 embarazadas chagásicas (15.9%), de las cuales se diagnosticaron 6 RN-ChC (4%). En el total de 968 RN estudiados se detectaron 12 RN infectados. El micro-hematócrito fue el método parasitológico de lectura rápida más efectivo para el diagnóstico de infección en nuestra serie. El par de reacciones serológicas específicas constituyó un criterio de mayor seguridad para el control y seguimiento de la infección congénita. Las expresiones clínicas más comunes de infección fueron hepatomegalia, esplenomegalia, ictericia, anemia y prematurez, con distintos grados de asociación. Se concluye que dadas las características clínicas de la enfermedad de Chagas congénita en nuestro medio, se impone como estrategia el diagnóstico serológico para la enfermedad de Chagas en todas las embarazadas y el control y seguimiento de sus RN hasta descartar o confirmar infección congénita.

The relative specificities and sensitivities of several serological assays for the diagnosis of Trypanosoma cruzi infection were estimated in Indian populations of Argentina and Paraguay. The results obtained with the assays, which proved to be most reliable, were used to study the distribution of the parasite in these populations. Serological evidence of T. cruzi infection was demonstrated in 256 (37.7%) of 679 Indians living in relatively small and isolated communities in the Salta province of northern Argentina and in western Paraguay, regions that are part of the tropical territory called Gran Chaco. In contrast, none of the 94 Indians examined in south-western Argentina was positive. Infection in the Gran Chaco Indians increased with age and clustered in families. Marked differences in seroprevalence were observed between the 16 Indian communities examined in Gran Chaco. These differences seem to be associated both with the risk of transmission from the sylvatic reservoirs of the parasite and with the frequency with which vector-spraying campaigns have been implemented.

We examined the possible role of altered humoral immunity in Chagas' disease by analyzing the effect of sera on the binding of radioligand to beta-adrenoceptors during the course of human Trypanosoma cruzi infection. We described two circulating IgG which bind with myocardial beta 1- and spleen cell beta 2-adrenoceptor. Both chagasic IgG against beta 1- and beta 2-adrenoceptors increased intracellular levels of cAMP, which could be blocked by specific beta 1- and beta 2-adrenoceptor antagonists. The IgG against the beta 1-adrenoceptor inhibited the action of norepinephrine on the contractility of atria. We also found differences in the distribution of beta 1- and beta 2-adrenoceptor antibodies in the course of infection. The anti-beta 2-adrenoceptor IgG appears during the acute stage, peaks on the group with less than 10 years of infection, and then decreases. The prevalence of anti-beta 1-adrenergic antibody is low in the acute stage, but it increases over time since infection, being higher in the group with more than 15 years of infection. The probable pathogenic role of both beta 1- and beta 2-adrenergic chagasic antibodies is discussed.

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